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8246788: ZoneRules invariants can be broken #2191

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@@ -1,5 +1,5 @@
/*
* Copyright (c) 2012, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -259,10 +259,12 @@ public static ZoneRules of(ZoneOffset offset) {
}

// last rules
if (lastRules.size() > 16) {
Object[] temp = lastRules.toArray();
ZoneOffsetTransitionRule[] rulesArray = Arrays.copyOf(temp, temp.length, ZoneOffsetTransitionRule[].class);
Comment on lines +262 to +263

This comment has been minimized.

@dfuch

dfuch Jan 22, 2021
Member

LGTM. Could be replaced by:

ZoneOffsetTransitionRule[] rulesArray = (ZoneOffsetTransitionRule[])lastRules.toArray(new ZoneOffsetTransitionRule[0]).clone();

if you wanted - but what you currently have is good for me.

This comment has been minimized.

@efge

efge Jan 22, 2021

Or even maybe rulesArray = lastRules.toArray(ZoneOffsetTransitionRule[]::new);?

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@dfuch

dfuch Jan 22, 2021
Member

Good point - but that would be:

ZoneOffsetTransitionRule[] rulesArray = lastRules.toArray(ZoneOffsetTransitionRule[]::new).clone();

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@stuart-marks

stuart-marks Jan 22, 2021
Author Member

Interesting. This last one is more concise, but it's a bit harder to reason about. The lastRules implementation could return an array of a type other than ZOTR[]. If it's unrelated or a supertype, this would result in ClassCastException -- probably not a problem. If it were a subtype of ZOTR[], this would get stored in the object's field. Is this a problem? Turns out it can't happen, since ZOTR is final. While not wrong, I don't think this is the right idiom.

It occurs to me that there should by another overload Arrays.copyOf(array, newType) that changes the type without changing the length. This would let us get rid of the local variable.

if (rulesArray.length > 16) {
throw new IllegalArgumentException("Too many transition rules");
}
this.lastRules = lastRules.toArray(new ZoneOffsetTransitionRule[lastRules.size()]);
this.lastRules = rulesArray;
}

/**
@@ -0,0 +1,85 @@
/*
* Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

package test.java.time.zone;

import java.time.*;
import java.time.zone.*;
import java.util.*;

import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertThrows;

/**
* @summary ZoneRules invariants can be broken.
*
* @bug 8246788
*/
@Test
public class TestMutableZoneRules {
static final ZoneOffset offset = ZoneOffset.ofHoursMinutes(1, 30);

static final ZoneOffsetTransitionRule rule1 =
ZoneOffsetTransitionRule.of(Month.APRIL, 2, DayOfWeek.TUESDAY, LocalTime.MIN, true,
ZoneOffsetTransitionRule.TimeDefinition.UTC, offset, offset, offset);

static final ZoneOffsetTransitionRule rule2 =
ZoneOffsetTransitionRule.of(Month.MARCH, 2, DayOfWeek.MONDAY, LocalTime.MIN, true,
ZoneOffsetTransitionRule.TimeDefinition.UTC, offset, offset, offset);

public void testMutation() {
ZoneOffsetTransitionRule[] array = { rule1 };
ZoneRules zr1 = ZoneRules.of(offset, offset, List.of(), List.of(), List.of(rule1));
ZoneRules zr2 = ZoneRules.of(offset, offset, List.of(), List.of(), new TestList(array, array.length));

assertEquals(zr2, zr1);
array[0] = rule2;
assertEquals(zr2, zr1);
}

public void testLength() {
ZoneOffsetTransitionRule[] array = new ZoneOffsetTransitionRule[17];
Arrays.setAll(array, i -> rule1);

assertThrows(IllegalArgumentException.class,
() -> ZoneRules.of(offset, offset, List.of(), List.of(), new TestList(array, 1)));
}

static class TestList extends AbstractList<ZoneOffsetTransitionRule> {
final ZoneOffsetTransitionRule[] array;
final int size;

TestList(ZoneOffsetTransitionRule[] array, int size) {
this.array = array;
this.size = size;
}

public int size() { return size; }
public ZoneOffsetTransitionRule get(int i) { return array[i]; }
public Object[] toArray() { return array; }

@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) { return (T[]) array; }
}
}